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2ND YEAR SYSTEMS: GI > Nutrient digestion > Flashcards

Nutrient digestion Flashcards

1
Q

what are the 3 monosaccharides?

A

glucose
galactose
fructose

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2
Q

what is the bond between two monosaccharides to form a disaccharide called?

A

glycosidic bond

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3
Q

where is amylase found

A

saliva

pancreas

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4
Q

Which type of glycosidic bond is found in starch?

A

alpha- 1,4

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5
Q

Which type of glycosidic bond is found in cellulose?

A

Beta- 1,4

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6
Q

In regards to the cells that line the intestine, what is the name for the side that faces inside the lumen

A

brush border/apical surface

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7
Q

In regards to the cells that line the intestine, what is the name for the side that faces into the lumen

A

apical membrane/brush border - specialised for absorption

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8
Q

what is required to absorb glucose?

A

Sodium

without the sodium potassium ATPase creating a Na+ gradient you cannot absorb glucose

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9
Q

what is the SGLT1 protein

A

A secondary active transporter molecule involved in glucose transport.

Takes Na+ and glucose into the cell. Gets it’s energy from the Na+ gradient created by the Na+/K+ pump on the basolateral membrane

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10
Q

what is GLUT-2 and what is it’s function?

A

It is a facilitator of diffusion. It is a carrier protein that sits in the basolateral membrane in the intestine

no energy required

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11
Q

what is the name of the fructose transporter in the small intestine?

A

GLUT 5

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12
Q

what is the main difference between glucose and fructose movement across the membrane?

A

when glucose moves across there is already sodium transport and so there is also water movement but with fructose there is no Na+ movement so no H20 movement

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13
Q

what are proteases or peptidases

A

Enzymes which hydrolyse peptide bonds and reduce proteins or peptides to amino acids

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14
Q

what is an endopeptidase

A

chops a peptide chain in half each time and reduces it in size that way

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15
Q

what is an exopeptidase

A

chops off the peptide bond at each end of the chain reduces it in size that way

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16
Q

dipeptide transport overview

A

NHE3 is on every epithelial cell. It takes in Na+ and pushes out H+ making acid microclimate outside cell

this drives PepT1 protein (dipeptide)

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17
Q

what form is almost all ingested fat in?

A

triacylglycerol

18
Q

where is fat digested and with which enzyme?

A 
small intestine
pancreatic lipase (water soluble)
19
Q

Is digestion of fat a slow or fast process?

A

slow - it can only take place at the surface of a fat/lipid droplet however enzyme catalyst can speed this up

20
Q

chemical equation for fat digestion?

A

triacylglycerol —> monoglyceride + 2 fatty acids

21
Q

what does emulsifcation require?

A

mechanical disruption of large lipid droplets ie vigorous mixing to break down fat droplets (smooth muscle contraction in our gut grinds and mixes lumenal contents)

emulsifying agent - ie bile salts and phospholipids, amphiphatic molecules

22
Q

what product enhances the process of absorption?

A

formation of micelles

23
Q

what is a micelle? role?

A

bile salt + monoglycerides + fatty acids + phospholipids

it transports fats to the surface (fat taxi) and releases them there. Micelles do not pass through (too big)– only the fat molecules

24
Q

where do FA’s and monoglycerides enter to when they enter an epithelial cell? what happens here

A

smooth endoplasmic reticulum (sER) they are reformed into triacylglycerols

25
Q

How are triacylglycerol droplets transported through a cell?

A

in vesicles formed from sER membrane

26
Q

What do chylomicrons pass into which transports them through in-between endothelial cells?

A

They pass into lacteals as they can’t get through the tight junctions of the capillary basement membrane.

So, this means the fat passes into the lymphatic system and not into the blood. The fat and fat soluble vitamins form chyle (this fluid contains lymph and emulsified fats, or free fatty acids).

Lymphatic vessels then transport them into the blood.

27
Q

name 4 fat soluble vitamins

A

A
D
E
K

28
Q

Name some water soluble vitamins. How are they absorbed?

A

B group
C group
Folic acid

Absorbed either by passive diffusion or carrier-mediated transport.

29
Q

What’s so special about vitamin B12?

A

Vitamin B12 is a large charged molecule that binds to intrinsic factor in the stomach.

Your body doesn’t produce B12 so it must be acquired from our diet.

It is absorbed in the distal ileum.

30
Q

What can B12 deficiency lead to?

A

Pernicious anaemia (failure of RBC maturation which is needed for efficient O2 carrying).

Treatment - injections

31
Q

How is iron transported through cells?

A

Iron is transported across the brush border membrane via DMT1 into duodenal enterocytes.

It is incorporated into ferritin (a protein-iron complex which acts to store iron intracellularly).

Unbound iron goes into the blood and binds to transferrin which takes it to the liver to prevent toxicity.

32
Q

what is ferritin?

A

intracellular iron storage - creates a cage like structure around the iron

33
Q

what does iron bind to in the blood?

A

transferrin

34
Q

What is the link between Hyperaemia and Anaemia with ferritin levels?

A

Hyperaemia => Increased ferritin levels = more iron bound in the duodenal enterocytes in protein-iron complex ie more iron being stored away. Can be released when needed.

Anaemia => Decreased ferritin levels so there is more iron released into the blood. RBCs need iron to form normally and carry O2 efficiently but in anaemia there aren’t enough RBCs for iron to attach to.

35
Q

Give 3 examples of emulsifying agents

A

Bile salts
Phospholipids
Amphiphatic molecules

36
Q

When/why does a micelle release its content/break down?

A

The micelle moves into acid microclimate which removes the charge off free fatty acids, destabilising their structure

The micelle then releases its contents which pass through the membrane without it.

37
Q

function of golgi apparatus in fat digestion

A

fat molecules are trafficked through the G.A which sorts them to make sure they go where they need to go.

38
Q

what is a lacteal and what is their importance

A

a branch of the lymphatic system

they take fat molecules into the lymphatic system and prevent them from getting into the blood circulation

39
Q

How does iron get absorbed in the duodenum?

A

it binds to DMT1 receptor in the brush border

40
Q

What is the basolateral membrane?

A

the term basolateral refers to the membrane on the base and sides of the cell. The basolateral membrane forms a barrier between the cell and the blood and/or other cells

2ND YEAR SYSTEMS: GI (38 decks)

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